Selecting a new image from a batch sets isLoading to true, but
handleImageLoad is never triggered so the image never displays.
Swapping to a different image from a batch is currently the only place
isLoading is set to true. This change, even if temporary, results in a
good chunk of dead code.
To my understanding, ImagePreviews are always object URLs and should
never need to load, so I don't foresee the loading placeholder being
needed here.
Resolves#6458
┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6521-Fix-inability-to-select-image-from-batch-in-vue-29e6d73d36508162abeaeece7c5e0eed)
by [Unito](https://www.unito.io)
